In this week's episode, '4,722 Hours,' written by Craig Titley ('Afterlife') and directed by Jesse Bochco ('Love in the Time of Hydra'), Simmons explains to Fitz everything that happened to her in the 4,722 hours she was on the alien planet. Among the highlights are the American astronaut also stranded on the planet named Will, played by guest star Dillon Casey (Nikita), and a manipulative creature that inhabits the planet's sandstorms. The tension-filled survival-story elements, along with the performances of Henstridge and Casey, help to make '4,722 Hours' by far one of the strongest episodes of season 3, and perhaps Agents of S.H.I.E.L.D. as a whole.

The Planet

Previously, we knew the planet was habitable, barren and desert-like, and in a different solar system than Earth. Though there have been theories about the planet's ties to the Marvel Comics, '4,722 Hours' fails to provide any connection to previously established Marvel Cinematic Universe mythos or the comic books. However, the episode does introduce a new mythology for the planet, one in which a team of astronauts sent by NASA in 2001 were nearly all driven insane by a mysterious force either within the planet itself or inhabiting its surface. In fact, Simmons witnesses the "it" creature, though it changes form as a way of manipulating her, but little is yet known about who or what the planet's other inhabitant may be.

Of course, everything learned about the planet is through Simmons' eyes, especially showcased in a scene early on in the episode when she records a note of the planet's gravity, terrain, oxygenation and lack of sunlight -- exactly as a scientist would do in this situation. Still, while Simmons has help learning about the planet from Will and his team's equipment, she doesn't learn much more than what she needs to survive and attempt to return home. So, this episode is focused on the vegetation and the predicted location of the portals rather than the planet’s larger implications for the MCU, but that doesn't necessarily indicate it's insignificant.

Will Daniels

Though the first quarter of the episode is centered solely on Simmons, she comes across stranded NASA astronaut Will Daniels by means of falling into a trap he has set in a cave system beneath the planet's surface. Casey's performance as Will works exceptionally well as the stoic, doom-and-gloom counterpart to Simmons' hopeful disposition, but even better is when the two are able to share lighter moments, such as when they discuss what food they miss from Earth or what they’ll do first when returning home: shower, eat or sleep. Of course, the story of the lone man left alone is space has been seen a number of times in science-fiction, and Will's story doesn't offer much differentiation from the standard. But, that being said, everything Simmons (and the viewer) knows about Will so far is what he's told her, which may not necessarily be the full truth -- as illustrated when he challenges her belief of his story.

Furthermore, with the introduction of Will, the episode deals with a man and woman left alone on a desert island, '4,722 Hours' takes a romantic turn. When she first lands on the planet, Simmons clings to the idea of Fitz as an anchor to keep her going, but through spending so much time with Will, she develops feelings for him as well. However, it's difficult to say whether these feelings are actually simple romance or a bond forged by thousands of hours spent working and living together, since the relationship takes a back seat to the larger issue of getting off the planet. Additionally, it may only be included to serve as a reason for Will's sacrifice at the end of the episode when he chooses to stay behind and fight the creature so that Simmons can go back through the portal with Fitz.

Still, the final scene of the episode, which depicts Will throwing away his empty gun as the sun disappears from the planet for another 18 years, leaves the character in a compelling, albeit bleak, situation. When he returns -- as he undoubtedly will -- it's uncertain what state he will be in, whether fully mad or maintaining the hope inspired by Simmons.

Simmons' Hope

Of course, Simmons is the star of the episode, sustained by Henstridge’s performance, as she struggles to keep the hope of Fitz's rescue alive, despite the hopelessness of the planet. In the early scenes of the episode, we see this in Simmons' efforts to find food and water as well as create a fire. Additionally, since the viewer knows how '4,722 Hours' ends -- with Simmons back on Earth and Will still trapped -- Simmons' hope also acts as the stakes of the story around which the tension of the episode is built. The question isn't whether Simmons will get home, since we know she will, it's how she does and whether she's forced to give up hope on Fitz.

Of course, once the dramatic arc of the episode is established, it takes a fairly standard route: Simmons sacrifices her hope in an effort to return home, but when that effort fails she's left searching for something else to keep her going, which happens to be acceptance of her new life with Will. Still, though the arc of the episode is largely predictable, the performance of Henstridge helps to bring enough emotion to give the storyline the weight that it needs to carry an entire 40-minutes of television. As evidenced by earlier episodes this season, Simmons has been and will likely continue to be the heart of Agents of S.H.I.E.L.D., grounding the show's more fantastic elements in human emotion and struggle.

Agents of S.H.I.E.L.D. has had plenty of balls up in the air in season 3, with the introduction of the ATCU, setting up the Secret Warriors, dealing with the number of new Inhumans, Hunter's mission of revenge, and Bobbi's recovery. Most recently, last week's episode set up new mysteries surrounding May's husband Dr. Gardner and the secret human identity of Lash. But, devoting an entire episode to Simmons' time on the alien planet gave the series a chance to take a dramatic risk, and it paid off. '4,722 Hours' is a strong hour of television that reminds viewers of what Agents of S.H.I.E.L.D. can achieve when given the opportunity.

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Share your thoughts on the episode and theories about the alienate planet in the comments below!

Agents of S.H.I.E.L.D. continues next Tuesday with ‘Among Us Hide…’ at 9pm on ABC. Check out a preview below: